feat(openmetrics): expose app information per-app

[nilsding]

• Resolves Expose installed app info metrics for each app #59718

Summary

With this change the app info metrics are exposed for each app, its value is the enabled state:

# TYPE nextcloud_app_enabled gauge
# HELP nextcloud_app_enabled Information about the installed Nextcloud applications
nextcloud_app_enabled{app_id="app_api",version="34.0.0-dev.0"} 1
nextcloud_app_enabled{app_id="cloud_federation_api",version="1.18.0"} 1
nextcloud_app_enabled{app_id="comments",version="1.24.0"} 1
[...]
nextcloud_app_enabled{app_id="user_status",version="1.14.0"} 0
nextcloud_app_enabled{app_id="weather_status",version="1.14.0"} 1
[...]

As this change makes the additional nextcloud_installed_applications metric obsolete as it can now be queried through Prometheus directly as followed, this metric has been dropped. (during testing of that I also noticed that the number of disabled apps is reported as -1 when all apps are enabled...)

label_replace(count by (instance)(nextcloud_app_enabled==1), "enabled", "true", "", "") or label_replace(count by (instance)(nextcloud_app_enabled==0), "enabled", "false", "", "")

TODO

• maybe come up with a different name for the metric?

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI